Introducing Polyolefins

1

Content

Synthetic polymers – Classification

– Global production

Polyolefins – Polyolefins family

– PE classification

– PP structures

– Key properties

– Additivation

– Application

– Global consumption

– Domestic production and consumption

2

Synthetic Polymers Classification by

Plastics Europe

Standard Plastics PE, PP, PVC, PS, EPS, PET (Bottle grade)

Engineering Plastics ABS, SAN, PA, PC, PBT, POM, PMMA, Other High Performance Polymers

PUR Polyurethanes

Thermoplastics Standard Plastics + Engineering Plastics

Plastic Materials Standard Plastics + Engineering Plastics + PUR

Plastics Plastic Materials + Others (Thermosets, Adhesives, Coatings, Sealants)

Elastomers Synthetic Elastomers (SBR, IR, IIR, BR, NBR, CR, Others)

Fibres PA, Polyester, Acrylic, Other Synthetic Fibres

Synthetic Polymers Plastic Materials + Fibres + Elastomers + Others (Thermosets, Adhesives, Coatings, Sealants)

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World Synthetic Polymers Production 2007

PUR Polyurethanes

Thermoplastics Standard Plastics+ Engineering Plastics

Others Thermosets, Adhesives, Coatings, Sealants

Elastomers Synthetic Elastomers (SBR, IR, IIR, BR, NBR, CR, Others)

Fibres PA, Polyester, Acrylic, Other Synthetic Fibres

Elastomers

4%

Others

14%

Fibres

13%

PUR

4%

Thermoplastics

65%

Polyolefins (PE+PP)

36%

Synthetic Polymers

production in 2007

approximately

315 million t globally

PE+PP represents

114 million t or 36%

of global Synthetic

Polymers production

4

World Plastics Production 1950 – 2011

Plastics=Synthetic Polymers less Elastomers and Fibres

1,7

47

99

204

245

280

14,5

41

90

115128

0

50

100

150

200

250

300

1950 1960 1970 1980 1990 2000 2010

Mil

lio

n t

Plastics

Polyolefins

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Polyolefins

PE and PP

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The Polyolefins Family

Polyethylene - PE

– LDPE

– Linear PE

HDPE/MDPE

LLDPE

Polypropylene - PP

– Homopolymers

– Copolymers

Random copolymers

Block copolymers (impact copolymers, heterophasic

copolymers)

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PE Classification by Density

HDPE/MDPE

LLDPE

LDPE

Schematic representation of various PE structures

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DENSITY COMONOMER PE GRADE

0,926-0,970 –/alfa-Olefins HDPE

0,926-0,940 alfa-Olefins MDPE

0,915-0,935 –/Acrylates/VA LDPE

0,915-0,926 alfa-Olefins LLDPE

PE grades by density

HDPE Chain Segments

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LLDPE Chain Segment

10

LDPE Chain Segment

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PP Structures

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Isotactic homopolymer Atactic homopolymer

Syndiotactic homopolymer

Block copolymer

PPPEEEEEEEPPPPPPEEEEEEEEPPP

Random copolymer

PPPPPEPPEPEPPEPPPPEPPPEPPPP

Isotactic PP Chain Segment

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Atactic PP

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Syndiotactic PP

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PP Homopolymer and Random Copolymer

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PP Block Copolymer

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18

Connection between properties

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Secondary or end use properties -melt index -mechanicals

• tensile strength • flexural modulus • impact strength

-ESCR

Primary properties -molecular weight -molecular weight distribution -comonomer content -stereoregularity (PP)

Molecular weight

Number average

• 𝑀𝑛 = 𝛴𝑁𝑖𝑀𝑖/𝛴𝑁𝑖

Weight average

• 𝑀w=ΣNiMi2/Σ(NiMi)

Polydispersity

• P=Mw/Mn

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Molecular weight distribution

number average

molecular weightweight average

molecular weight Mn

Mw

molecular weight

number of

molecules

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Bimodal Polymer Molecular structure vs. properties

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R1 R2

Mw

N

Low Mw homopolymer:

- increased crystallinity →

higher stifness

- good processability

high Mw copolymer:

- tie chains between crsytals

- elastic properties

- high mechanical strength

- high toughness

- excellent ESCR

SC

B/1

00

0C

Comonomer built into

high Mw molecules:

- impact strength

- ESCR

tie molecules

Crystalinelayers

m(lo

g M

)

log M

Crystaline layers: Stiffness

Tie Molecules: ESCR, Impact Strength

SCB

Crystallite

Melt Index

Melt index – measure of ease of flow of polymer melt One kind of reciprocal viscosity

Instead of determination of molecular weight

Fast standard method to

control quality

compare products

Melt index and molecular weight High melt index=low viscosity=low molecular weight

Low melt index=high viscosity=high molecular weight

Non Newtonian behaviour Melt index (viscosity) depends on load

Melt indices measured at different loads give indication on molecular weight distribution

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Density (D)

– Important for PE - strong influence on properties

– Depends on comonomer content (SCB=short chain

branching): more SCB = lower D

– Longer comonomer chain = lower D

– Comonomers tend to incorporate into lower Mw

molecules deteriorating organoleptic properties

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tie molecules

Crystalinelayers

m(l

og

M)

log M

Crystaline layers: Stiffness

Tie Molecules: ESCR, Impact Strength

SCB

Crystallite

Crystalline layers: stiffness

Tie molecules: ESCR, impact strength

Mechanical Properties 1

Tensile strength (TS)

– Higher crystallinity results on higher TS

– TSPP>TSHDPE>TSLDPE

– TS measured on both machine (MD) and transversal direction (TD) on film

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Mechanical Properties 2

Impact strength (IS)

– Ability to withstand shock loading

– Higher Mw = higher IS

– Lower D = higher IS

– Dart drop: special impact test for film grades

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Mechanical Properties 2

Flexural modulus (FM)

– Measure of stiffness – higher FM means higher stiffness

– Higher D = higher FM

– FMPPHOMO>FMPPHECO>FMPPRACO

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ESCR – Environmental Stress

Cracking Resistance

– Ability to withstand cracking under load in chemicals

– Mainly used for PE - very important for blow moulding and pipe grades

– Lower D = higher ESCR

– Higher MW = higher ESCR

– Role of comonomer distribution – comonomers built into high MW molecules give very good ESCR

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Additivation

Polyolefins mainly PP and HDPE need different additives to meet end use requirements. Typical concentration: some hundreds through some thousands ppm (1 ppm=1 g/t)

Typical polyolefins additives

– Stabilizers – to protect polymer from oxidative degradation during

Processing – melt stabilization (high temperature, short time + oxygen)

Long term use

– thermal stabilization (low temperature, long time + oxygen)

– UV stabilization – ( low temperature, long time, UV light + oxygen)

– Processing aids and property modifiers

Slip agents – to reduce friction during processing

Antistatic agent – to prevent build up of electrostatic charging

Antiblocking agent – to avoid sticking of film layers

Nucleating agents – to improve stiffness

Clarifying agents – to increase product transparency

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Application

0%

20%

40%

60%

80%

100%

LDPE LLDPE HDPE PP

others

pipe and conduit

extrusion coating

injection moulding

blow moulding

fibre

film

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Global Consumption

0

10

20

30

40

50

60

70

80

90

1975

1977

1979

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

2009

2011

mil

lió

to

nn

a

PE

PP

30

Per Capita Consumption

0

5

10

15

20

25

30

35

North

America

South

America

Western

Europe

Africa Asia Global

kg

per c

ap

ita

PE

PP

31

Domestic Production and

Consumption

55

105

155

205

255

305

355

405

455

505

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

PE production

PE consumption

PP production

PP consumption

32